1. Field of the Invention
The present invention generally relates to a system and method for administering focused energy to a body using either a single energy applicator or multiple microwave applicators, warmed fluid and compression in order to treat visible tumors and microscopic malignant and benign cells in tissue with thermotherapy. In particular, the present invention relates to a transurethral catheter for microwave thermal and warming therapy with compression of prostate tissue adjacent a urethra to create a biological stent.
2. Description of the Prior Art
In order to treat the prostate with thermotherapy, it is necessary to heat a significant portion of the prostate gland while sparing healthy tissues in the prostate as well as the surrounding tissues including the urethral and rectal walls of a patient. The prostate gland encircles the urethra immediately below the bladder. The prostate, which is the most frequently diseased of all internal organs, is the site of a common affliction among older men, benign prostatic hyperplasia (BPH), acute prostatitis, as well as a more serious affliction, cancer. BPH is a nonmalignant, bilateral nodular tumorous expansion of prostate tissue occurring mainly in the transition zone of the prostate. Left untreated, BPH causes obstruction of the urethra that usually results in increased urinary frequency, urgency, incontinence, nocturia and slow or interrupted urinary stream.
Recent treatment of BPH includes transurethral microwave thermotherapy in which microwave energy is employed to elevate the temperature of tissue surrounding the prostatic urethra above about 45° C., thereby thermally damaging the tumorous prostate tissue. U.S. Pat. Nos. 5,330,518 and 5,843,144 describe methods of ablating prostate tumorous tissue by transurethral thermotherapy, the subject matter of which is incorporated by reference. However, improvements still need to be made in this type of therapy to further maintain or enhance the patency of the urethra after the thermotherapy treatment. In particular, urine flow is not always improved despite ablation of the tumorous tissue causing constriction of the urethra because edema produced by the transurethral thermo-therapy treatment blocks the urethra passage resulting in patients treated by the above methods to be fitted with catheters for several days or weeks after the thermotherapy treatment.
U.S. Pat. Nos. 5,007,437, 5,496,271 and 6,123,083 disclose transurethral catheters with a cooling balloon in addition to the anchoring or Foley balloon and are incorporated by reference herein. However, these patents circulate fluid, which acts as a coolant for removing heat preferentially from the non-prostatic tissue adjacent thereto, through the cooling balloons. The '083 patent further discloses the use of a thermotherapy catheter system taught by U.S. Pat. No. 5,413,588 that employs chilled water between about 12° C.-15° C. as the coolant. Chilled water significantly cools the urethra adjacent the cooling balloon. Likewise, the '271 patent describes a coolant as the fluid to keep the urethral wall temperatures cool. This chilling of the urethra does not aid in maintaining an opening within the heated urethra after the cooling balloon is removed, and reduces the therapeutic effect in the tissue immediately adjacent the urethral wall.
Another known alternative to thermal surgery, as described in U.S. Pat. No. 5,499,994, is to insert a dilation balloon in the urethra and to expand the dilation balloon to compress the obstructed urethra. However, the expansion of the dilation balloon occurs over 24 hours and the patient still is not cured of the diseased prostate and can cause adverse effects (e.g., tearing of the urethral walls). U.S. Pat. No. 6,102,929 describes a post-operative procedure where the prostate tissue is expanded after the surgical procedure to enlarge the urethra to enable a patient to void comfortably. This expansion requires insertion of another device and requires the device to remain in the patient for a day or more.
In view of the fact that post-treatment catheters or other devices are still considered necessary by the medical community, further improvements are needed in thermotherapy to avoid the obstruction caused by edema and to maintain and enhance the opening of the urethra.